An actuator for an optical pickup includes a magnetic circuit having a structure in which coils to drive an objective lens in one direction selected from a focusing, tilting, or tracking directions, and magnets to drive the objective lens in the other directions. The coils and magnets are installed on the bobbin. The actuator for an optical pickup reduces the number of wires required for 6-axis direction driving, thereby making assembly easy. The actuator includes magnets, yokes, and coils in the bobbin, thereby reducing the mass of the bobbin, improving sensitivity, and increasing the efficiency of magnetic force.
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20. An actuator to hold a lens, comprising:
a bobbin to hold the lens; a base including a mount; a magnetic circuit formed at said bobbin and at said base, said magnetic circuit comprising bobbin coils and bobbin magnets on said bobbin and which use corresponding base magnets and base coils on said base to selectively move and/or rotate said bobbin along ones of six degrees of freedom; and holders coupled between the mount and said bobbin to support said bobbin such that said bobbin moves relative to said base and to provide current to the bobbin coils.
1. An actuator usable in an optical pickup, the actuator comprising:
a bobbin to hold an objective lens; a base including a mount; holders coupled between the mount and said bobbin to support said bobbin such that said bobbin is movable with respect to said base; and a magnetic circuit installed at said bobbin and at said base to drive the objective lens in focusing, tracking, and tilting directions; wherein: said magnetic circuit comprises: bobbin coils to drive the objective lens in one direction selected from focusing, tilting, and tracking directions, and bobbin magnets to drive the objective lens in the other directions selected from the focusing, the tilting, and the tracking directions, and the bobbin coils and the bobbin magnets are installed on said bobbin. 2. The actuator of
the bobbin coils comprise first and second coils installed at opposite first sides of said bobbin and are used to drive the objective lens in the focusing and the tilting directions; the bobbin magnets comprise tracking magnets installed at corresponding opposite second sides of said bobbin and are used to drive the objective lens in the tracking direction; and said magnetic circuit further comprises: first and second magnets installed on said base opposite the corresponding first and second coils, tracking coils installed on said base opposite the corresponding tracking magnets. 3. The actuator of
the bobbin magnets comprise first and second magnets installed at corresponding opposite first sides of said bobbin and are used to drive the objective lens in the focusing and the tilting directions; the bobbin coils comprise tracking coils installed at corresponding opposite second sides of said bobbin and are used to drive the objective lens in the tracking direction; and said magnetic circuit further comprises first and second coils installed on said base opposite the corresponding first and second magnets, and tracking magnets installed on said base opposite the corresponding tracking coils. 4. The actuator of
5. The actuator of
6. The actuator of
7. The actuator of
8. The actuator of
9. The actuator of
10. The actuator of
11. The actuator of
12. The actuator of
13. The actuator of
14. The actuator of
15. The actuator of
16. The actuator of
internal yokes disposed on said base between the objective lens and the corresponding bobbin coils, and external yokes disposed on said base and adjacent the corresponding base magnets.
18. The actuator of
said holders comprise less than six wires and provide current to the bobbin coils, and said bobbin holds less than four bobbin magnets.
19. The actuator of
the focusing direction is substantially parallel with an optical axis of the objective lens, the tracking direction is perpendicular to the focusing direction, and the tilting direction rotates about a rotational axis perpendicular to both the focusing and tracking directions.
21. The actuator of
22. The actuator of
23. The actuator of
24. The actuator of
27. The actuator of
28. The actuator of
29. The actuator of
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This application claims the benefit of Korean Application No. 2001-31970, filed Jun. 8, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an actuator for an optical pickup, and more particularly, to an actuator for an optical pickup having an improved structure in which assembly is easier and sensitivity is increased.
2. Description of the Related Art
An actuator for an optical pickup drives an objective lens in a focusing direction, in a tracking direction and/or in a tilting direction. Actuators for optical pickups include moving coil type actuators, which have a coil installed on a bobbin, and moving magnet type actuators, which have a magnet installed on a bobbin.
Referring to
In the conventional moving coil type actuator for an optical pickup shown in
Since the bobbin 14 is light in weight, the conventional moving coil type actuator has a high sensitivity. However, since six wires (four wires 19 and two wires 19a) are required to drive the bobbin 14 in focusing, tracking, and tilting directions, the conventional moving coil type actuator has a complicated and cluttered structure and is difficult to assemble. That is, it is very difficult to attach six wires (four wires 19 and two wires 19a) to the narrow sides of the bobbin 14, resulting in an increase in defects.
Referring to
As shown in
To solve the above and other problems, it is an object of the present invention to provide an actuator for an optical pickup having an improved structure which is easier to assemble than a conventional moving coil type actuator for an optical pickup, and is more sensitive and uses magnetic force more efficiently than a conventional moving magnet type actuator for an optical pickup.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, there is provided an actuator for an optical pickup according to an embodiment of the invention that includes a bobbin on which an objective lens is installed, holders coupled between a mount installed on a base and the bobbin to support the bobbin such that the bobbin is movable with respect to the base, and a magnetic circuit installed in the bobbin and in the base to drive the objective lens in focusing, tracking, and tilting directions, wherein the magnetic circuit includes coils installed on the bobbin and which drive the objective lens in one direction selected from focusing, tilting, and tracking directions, and magnets installed on the bobbin to drive the objective lens in another direction selected from the focusing, the tilting, and the tracking directions.
According to an aspect of the invention, the magnetic circuit includes first and second coils installed at opposite first sides of the bobbin and are used to drive the objective lens in the focusing and the tilting directions, first and second magnets installed on the base opposite the corresponding first and second coils, tracking magnets installed at opposite second sides of the bobbin and are used to drive the objective lens in the tracking direction, and tracking coils installed on the base opposite the corresponding tracking magnets.
According to another aspect of the invention, the magnetic circuit includes first and second magnets installed at opposite first sides of the bobbin and are used to drive the objective lens in the focusing and the tilting directions, first and second coils installed on the base opposite the corresponding first and second magnets, tracking coils installed at opposite second sides of the bobbin and are used to drive the objective lens in a tracking direction, and tracking magnets installed on the base opposite the tracking coils.
According to yet another aspect of the invention, the holders comprise wires or leaf springs and are used as paths to apply current to the tracking or first and second coils installed on the bobbin.
According to still another aspect of the invention, the actuator further includes yokes to improve the efficiency of a magnetic force of the magnetic circuit.
According to still yet another aspect of the invention, the actuator further includes internal yokes installed on the base opposite the corresponding first and second coils, or external yokes installed on the base opposite the corresponding first and second magnets installed opposite the first and second coils.
According to a further aspect of the invention, the actuator further includes internal yokes installed on the base opposite the corresponding tracking coils, or external yokes installed on the base opposite the corresponding tracking magnets installed opposite the tracking coils.
According to a yet further aspect of the invention, the first, second, and tracking coils comprise fine pattern coils (FPCs).
According to a still further aspect of the invention, the actuator includes less than 6 wires connected to the bobbin.
According to a still yet further aspect of the invention, fewer than 4 magnets are on the bobbin having the fewer than 6 wires.
The above and other objects and advantages of the present invention will become more apparent and more readily appreciated by describing in detail embodiments thereof with reference to the accompanying drawings in which:
Hereinafter, embodiments of the present invention will be described in detail the invention with reference to the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.
Referring to
Internal yokes 65 are installed on the base 30 opposite the corresponding focusing and/or tilting coils 31. External yokes 63 are installed on the base 30 opposite the corresponding focusing and/or tilting magnets 33. The focusing and/or tilting magnets 33 are installed on the external yokes 63 according to an embodiment of the invention, but need not be so installed in all aspects of the invention. Four holders 39 movably support the bobbin 34 with respect to the base 30. One end of the holder 39 is coupled to the bobbin 34, and the other end of the holders 39 is coupled to a mount 32 installed on the base 30. The holders 39 are used as paths to apply current to the focusing and/or tilting coils 31 installed on the bobbin 34. According to embodiments of the invention, the holder 39 comprises wires and/or leaf springs.
An objective lens 71 is installed on the bobbin 34. The bobbin 34 is driven in a focusing and/or tilting direction by the interaction of current flowing through the focusing and/or tilting coils 31 with the magnetic field of the focusing and/or tilting magnets 33. When force is simultaneously applied to the focusing and/or tilting coils 31 in a same direction by a synchronous driving method, the objective lens 71 is driven in a focusing direction. When force is applied to the focusing and/or tilting coils 31 in different directions by an asynchronous driving method (i.e., force is applied upward to a focusing and/or tilting coil 31 and force is applied downward to the other focusing and/or tilting coil 31), the objective lens 71 is rotated in a tilting direction. When force is simultaneously applied to the tracking magnets 37 and the tracking coils 35 in a same direction by a synchronous driving method, the objective lens 71 is driven in a tracking direction. In this way, the bobbin 34 is driven in three degrees of freedom. However, it is understood that the bobbin 34 could be driven in additional ones of the degrees of freedom using other combinations of applied forces.
Since the present invention includes coils 31 and magnets 37 on the bobbin 34, 6-axis direction driving is possible using only four holders 39. Further, when the holder 39 is a leaf spring instead of a wire, the leaf spring can be integrated into the base 30 according to an embodiment of the invention.
A neodymium (Nd) magnet, which is quite appropriate for a small size, is used as one of the magnets 33, 37 according to another embodiment of the invention. Also, a multiple magnet is used as one of the magnets 33, 37 so as to increase magnetic flux density in an air gap according to a further embodiment of the invention. However, other types and forms of magnets 33, 37 can be used.
The coils 31, 35 comprise conventional wound coils and/or fine pattern coils (FPCs) according to embodiments of the invention.
Referring to
The principle of driving in a focusing and/or tilting direction and in a tracking direction is the same as in the embodiment shown in FIG. 3. Specifically, the actuator for an optical pickup that includes the focusing and/or tilting coils 31 and the tracking magnets 37 installed on the bobbin 34 is included in the embodiment shown in FIG. 3. The internal yokes 65 are included opposite the focusing and/or tilting coils 31, and the external yokes 63 are included opposite the focusing and/or tilting magnets 33, resulting in obtaining paths for magnetic flux. The yokes 63, 65 need not be used in all aspects of the invention. The actuator for an optical pickup that includes the tracking coils 45 and the focusing and/or tilting magnets 43 installed in the bobbin 44 are included in the embodiment shown in FIG. 6. The internal yokes 75 are included opposite the tracking coils 45, and the external yokes 73 are included opposite the tracking magnets 47, resulting in obtaining paths for magnetic flux. The yokes 73, 75 need not be used in all aspects of the invention.
The arrangement of magnets 31, 37 and coils 33, 35 of the actuator will be explained with reference to the embodiment of the present invention shown in
Referring to
The middle portion of each of the magnets 33, 37 is a neutral zone that a magnetic force does not affect. Higher magnetic flux is distributed at both ends of each of the magnets 33, 37. According to an embodiment of the invention the magnets 33, 37 are multiplied at opposite ends of each of the magnets 33, 37, resulting in higher magnetic flux density in an air gap and thus a greater effect on the coils 31, 35.
According to the present invention, coils and magnets are on the bobbin, thereby reducing the number of wires compared with the conventional moving coil type actuator for an optical pickup having only coils on a bobbin, and making assembly easy. Further, the mass of the bobbin is reduced compared to the conventional moving magnet type actuator for an optical pickup, thereby improving sensitivity, and further includes yokes on the base, thereby increasing the efficiency of magnetic force.
In the actuator for an optical pickup according to the present invention, assembly of the actuator is simpler than the assembly of the conventional moving coil type actuator for an optical pickup, and the mass of the bobbin is reduced compared with the mass of the conventional moving magnet type actuator for an optical pickup, thereby improving sensitivity of the actuator for an optical pickup. And if the actuator further includes yokes, magnetic force is used more efficiently. It is further understood that the actuator could be used in devices other then optical pickup assemblies, and that the bobbin could be made to move in others of the six degrees of freedom.
While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the accompanying claims and equivalents thereof.
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